Mechanical apparatus for developing strength, flexibility, and agility have been known and used from antiquity to the present. In the past 50 years, machines have been created that may be configured to provide specific resistance and tailored movement for many individuals having different muscle strengths, range of movement, and exercise goals. By being configurable for a variety of possible users, a single machine may replace or be substituted for a range of potential exercises that formerly were done on a number of single-use machines. The first of such machines were normally dedicated to improving arm strength or leg strength. Exercises involving the stomach or abdominal muscles were generally carried out by lying on a mat on a floor, and using the body's own resistance to work abdominal muscles. Such exercise, however, was limited in the range of movement and muscle groups that could be worked. Accordingly, there is a need for apparatus that permits the exercise of stomach or abdominal muscles over a range of movement and motion, and that permits the user to work all muscle groups within that part of the body.